Koala Physiology and Behavior by Kunal Thakur
The koala, phascolarctos cinereus, is a species which can only be found in Australia and is part of the marsupial family which give birth to undeveloped young which climb onto the pouch and latch on to the teat until complete development. As an arboreal marsupial herbivore, the animal lives in Eucalypt forests along the Eastern region of Australia including Queensland, New South Wales, Victoria, and South Australia. Descending from a group of much bigger animals in the Australian environment, the koala is the only remaining member of the Phascolarctidae family with its closest relatives being the wombats. In order to survive, the koala has evolved specifically to become the only mammal that can survive on leaves of the Eucalyptus tree alone. Because of the low energy and nutrient output that the Eucalyptus tree leaves provide, the koala has had to evolve several physiological and behavioral traits in order to successfully use the tree as a source of food. In order to make the most of the food source, the Koalas only eat from 10% of the 600 different species of the Eucalyptus tree with an even stronger preference of only 5% to maximize the number of nutrients which can be obtained as some species of the tree are more nourishing than others. The leaves of the specific species are chosen for their protein content and low indigestible fiber and lignin amounts. The koala has also evolved a liver which works to isolate and excrete the toxins which make the Eucalyptus tree indigestible for other animals. With an extremely long digestive process, the koalas use hindgut fermenters and long caecum with specific bacteria to digest the fiber of the Eucalyptus tree. To raise the young, the koala mothers must make a “pap” which consists of a mixture of milk and tree leaves to feed the koala young to make sure they become used to toxins and bacteria which comes with the Eucalyptus leaves. Behavior and lifestyle of the Koala has also been adapted to their diet. Because of the lack of nutrients of the leaves of the Eucalyptus tree, the koalas follow a low energy diet and can spend up to 21 hours a day resting. Their brain has evolved to become much smaller to conserve energy for the animal and this causes the species to have no complex communication and live in solitude not doing much other than eating and sleeping. There can be no extended maternal care because of the energy required to take care of the young and the mother will leave as soon as the developing koalas can eat the leaves of the Eucalyptus tree. With curved, sharp claws and opposable digits, the koala is well adapted to climb trees and also grasp branches on the Eucalypt. The animal has incisors and cheek teeth which allow for it to take in leaves and cut and grind the leaves down which leads to better digestion. As the koala has evolved very specifically to match its niche diet of Eucalyptus tree leaves, the animal does not have many other ecological interactions. The koala has few natural predators as it spends most of its life up in the high branches of the Eucalyptus trees and also does not perform any other role in the Australian ecosystem. By fitting into a very specialized role through repeated evolution, the koala has eliminated its ecological role in the Australian environment.
Koala Conservation by Lin Cao
Found exclusively in Australia, koalas have become an icon for the country and its unique wildlife. They are under federal protection, and it is illegal to hunt and kill koalas. However, they are under pressure from many other threats, and their populations have crashed by up to 80% in certain urban areas.
Though koalas are protected, their habitats are not. Habitat fragmentation is a major issue, and as development projects force koalas into smaller areas, stress and overcrowding have caused additional problems. Chlamydia easily spreads among tightly packed individuals, and the disease eventually leaves individuals blind and vulnerable to many other dangers. Deaths from car collisions and encounters with dogs and cats also increase as contact between koalas and humans increases. Another hazard for koalas is high intensity fires. After a long period of fire suppression in Australia, many areas of eucalypt forest have high amounts of unburned fuel left, and accidental or sudden fires may flare out of control and kill koalas who are unable to escape. Climate change represents a major challenge for koalas. Koalas exclusively eat eucalyptus leaves, which are quite nutrient poor. They consume massive amounts of leaves each day to acquire nitrogen for amino acid and protein synthesis, and the leaves also provide a source of water. However, climate change has created a shift in eucalyptus leaf content. Nitrogen levels are decreasing while carbon levels increase. Water content has also decreased. Both of these changes place additional pressures on koalas and their current feeding habits.
With the challenges they are facing, koala conservation has come under the spotlight and generated a few debates. Koalas play no ecological role. For instance, they have few natural predators and do not help propagate any plants. Much of the push for koala conservation comes from public sentiment for koalas as an icon for Australia rather. However, some wonder if there has been too much of a focus on iconic or charismatic species like koalas when there are much more vulnerable or important species. For instance, termites play an important ecological role in Australia and are facing challenges as humans brand them as pests and work to eradicate them, but there are few efforts to protect them or increase awareness of their importance. In contrast, there are many koala advocacy and conservation groups, and much of the general public has some knowledge about koalas. Though the debate rages on, one potential role for the koala is as an ambassador species. Certain organizations use more iconic animals to engage the general public and then use that engagement to promote other species. Koala conservation can also have umbrella effects. To save a koala, a eucalyptus forest has to be saved, and other species dependent on that forest may be saved as well. Koala conservation is also a good idea from an economic standpoint. Koala-related tourism is an important source of revenue, and estimated expenditure on zoo visits, koala photos, and koala souvenirs is nearly $336 million per annum. Finally, some argue that koalas should be conserved because only human error has caused their populations to decline. They came to exist in Australia and it is only fair to preserve their natural status. While there is some debate around koala conservation, it is clear that as koala populations continue to respond to environmental pressures, koala management attitudes strategies will have to adapt as well.
Koala Population Field Work by Ben Lasley
Today we worked with Jules from the Billabong Sanctuary and Rachel from the Koala Park to continue research that James Cook University started on Koala populations on Magnetic Island. After breakfast, we biked to the first of the two sites and learned about the ongoing experiment and the procedures. The fifteen were split into three teams of five, with four in each team designated as collectors and one designated as the “sniffer” for the team. The sniffer was tasked with differentiating old koala scat from new koala scat. The new koala scat, which is up to 57 days old, smelled faintly of eucalyptus leaves, whereas the old scat, greater than 57 days, was odorless. The different teams laid out fifty meter by 1.9 meter transects through the bush by attaching rope to a beginning point, like a tree, and measuring 50 meters onward. The width was controlled by a 1.9 meter stick that was split evenly so that .95 meters was on either side of the rope. Two teams of two started on both sides of the 50 meters and were given gloves and miniature rakes to comb through the underbrush.
The teams were advised on the threat of death adders and taught the procedures if someone was bitten by a snake. The three teams were given one hour to hopefully finish the transect and quantify the number of old and new scat. As the teams would comb through the scat, the sniffers would be behind them going through the retrieval bags and sorting the koala scat into old and new bags. Additionally, collectors would occasionally pick up misshaped scat, only to discover that it was wallaby scat. The wallaby scat definitely did not smell of eucalyptus leaves. As the teams progressed throughout the transects, they encountered ferocious green ants and when their nests were slightly disturbed, they poured out and bit numerous people.
Another component of the transect was the identification of different trees within the various transects. While one group only had Morleton Grey Ash and Popular Gum trees, other groups had Red Gum Eucalyptus trees, which are the favorite food of the koalas. At the end of the hour, two groups had finished, while the other group had sixteen meters left in the transect. As the three groups complied the number of scats, one group only had 190 koala scats, while the other two groups had over 400 koala scats each. This was attributed to the various species in the transect, with one transect having a large and mature Red Gum, the favorite of koalas.
After cleaning up the site, the group biked to a koala hotspot. They were able to see a total of 6 Koalas, including a mother and her joey, two solitary koalas, and a mother and offspring pair that had recently split off. After returning to the hostel, the data was interpreted and explained to the team. The data would be compiled into a spreadsheet and then fed into several equations to determine the population of koalas on Magnetic Island and the migration patterns depending on the season. The field work was dirty and sometimes smelly, but the experience was worth it.
A Look at Koala Population Studies on Magnetic Island
By Danny Oh
On July 2nd, the UNC Study Abroad group went to an open mixed eucalyptus forest to assist in koala population size studies. We helped Jules Funnell, a ranger at the Billabong Sanctuary, perform the fecal standing crop method for estimating the population size of koalas at the site. This was part of James Cook University’s initiative in beginning a long-term population study of koalas on Magnetic Island. The study began last year, and since then, there have been several ecotourism groups that have contributed to the growing dataset.
Koalas did not previously exist on Magnetic Island: European colonization of mainland Australia led to the development of the koala fur trade. By 1924, Koalas were extinct in South Australia, and the fur trade had moved up to Queensland. In 1919, the QLD government announced a 6-month open season on koalas, and one million koalas were killed in that season alone. In 1927, the season reopened and over 800,000 koalas were killed within one month. Public outrage led the government to declare koalas a “protected species”, and koalas were introduced on islands, such as Kangaroo Island and Magnetic Island, as insurance populations in the late 1930s. Although they provide no ecological role within the ecosystem, they are valued highly within the ecotourism industry, bringing in a A $3.2 billion profit annually and 30,000 jobs. Koala population studies have been implemented in several states of mainland Australia, and the populations were carefully monitored every several years. However, no one knew exactly what the koala population size was on Magnetic Island.
In 2011, McGregor et. al. did the first koala population studies on Magnetic Island in the peer reviewed article, The Distribution and Abundance of an Island Population of Koalas (Phascolarctos cinereus) in the Far North of Their Geographic Range. They performed the Fecal Standing Crop Method (FSCM), where they used GPS designated points along with 100 m transects and collected koala scat. The scat was then separated based on smell of eucalyptus: the new scat retained the smell of eucalyptus (smell lingered for approximately 57 days) while the old scat lost its smell. In the article, 285 transects were analyzed over a time period of 656 hours. The FSCM was validated in a previously published article by CSIRO, and it is favored due to the solitary lifestyle of koalas. They estimated between 800 to 900 koalas on the island today.
It is difficult to estimate the koala populations from the UNC studies. Unfortunately, we do not have the literature that goes into the mathematics in translating scat counts to koala population size. However, we do see the merits of the research: the McGregor 2011 paper did not collect data in disturbed urban areas, which is where we collected scat. The population trends of koalas in urban areas could be valuable in determining their resiliency with encroaching urbanization. In addition, this data is still at its initial steps, since only two years of data have been collected so far. Population dynamics studies use data sets that are collected over a long time. The data set can then be used to observe seasonal variation and population trends of koala population size on Magnetic Island.
Even though we couldn’t really get the actual koala population size, we felt that we had made a great contribution in a growing data set for future groups visiting Magnetic Island. Though the koalas do not provide an ecological role, I did witness their value in the ecotourism industry: I got my picture taken with Claudia at Bungalow Bay Koala Village, and it really is something I will cherish from this trip.
Learn more about McGregor’s koala population study:
Caption: This shows the koala habitats that are projected to disappear within the next half century due to urbanization of coastal areas of East Australia.